1. Technical Field
This invention relates to an electronic parts mounting device such as a chip mounter and the like.
2. Prior Art
A chip mounter is publicly known for locating and mounting electronic parts such as a diode, a register, an LSI and the like on a printed circuit board and the like. FIG. 7 is a schematic view of a typical prior art chip mounter. In the drawing, shown at numeral 2 is a tape reel for storing electronic parts. The electronic parts are usually mounted and stored on a surface of the tape which is usually formed of a paper or a plastic material, and the tape is usually wound on a tape reel. A parts supply unit 4 is provided near to the tape reel 2, for retaining the tape reel 2 and supplying the electronic parts being stored on the tape by feeding out the tape sequentially and intermittently at a distance at which the electronic parts has been mounted on the tape. Further, there are provided on the chip mounter conveyer means including such as a belt conveyer for carrying in such as a printed circuit board (substrate) 6 to a predetermined location and carrying out the substrate 6 when electronic parts have been mounted thereon.
There are provided parts-absorption-mounting head device 10 for mounting electronic parts on the substrate 6 being located standstill at a predetermined position. Usually, 60-80 sets of parts supply units 4 are provided for mounting a plurality of various electronic parts on a single substrate 6. The parts-absorption-mounting head device 10 is mounted on an X-Y drive mechanism 12 which includes an X transfer arm 12a movable in the X-direction and a Y transfer arm 12b movable in the Y-direction.
The parts-absorption-mounting head device 10 receives electronic parts from the parts supply unit 4 by vacuum absorption, controls the attitude of the absorbed parts to the center of a nozzle, and mounts the parts on the substrate 6. Such device is disclosed in, e.g., Japanese Patent Publication No. 3-15359 (1991) (U.S. Pat. No. 4,135,630) and the like, and FIG. 8 shows a schematic view. Two pairs of locators 14 are mounted on a rotatable hollow spindle 16, and the pairs of the locators 14 (only one pair is shown in the drawing) can open and close with respect to the axis of the spindle 16 and in the directions orthogonally intersecting with each other, such that when the locators are closed the attitude of the parts 18 absorbed and retained on the tip end of the spindle 16 is corrected. The two pairs of the locators 14 are fixed in one direction with respect to the rotation of the spindle 16, and each locator 14 is urged in the closing direction by independent spring not shown in the drawing, and the attitude of the parts 18 is corrected when the locators are moved in the closing directions. Further, there are provided a casing 20 which covers the spindle 16, and a cam 22 being slidable in the vertical directions with respect to the casing 20. When the cam 22 is moved downward by a cam driving means not shown in the drawing, the lower end of the cam 22 contacts with the upper ends of the locators 14 to move them in radially outward directions.
However, in such prior art devices, there are the following problems. First, the two pairs of the locators 14 are fixed in one direction with respect to the rotation of the spindle 16 (the locators 14 do not rotate when the spindle 16 is rotated), thus, in mounting a parts on the substrate 6 at an angle of 30 degrees, for example, it is required to rotate the spindle by the desired angle of 30 degrees after the parts is located by the locator 14, thus, there is a tendency that the located angle is displaced. It will be noted that in mounting the parts at an angle either of 0 degree, 90 degrees, 180 degrees and 270 degrees, it is not required to rotate the spindle after the parts is located by the locator 14.
Second, each locator 14 is urged in the closing direction by an independent spring (not shown), thus, when the spring force of respective springs are not equal with each other, the parts 18 is displaced in the lateral direction, as shown in FIG. 9. Accordingly, the parts 18 cannot be located at the center of the nozzle. In particular, the spring force of the respective springs cannot be adjusted equally even though the springs are formed of coil springs or leaf springs, and it is not possible to overcome the time-dependent change, thus, even if the spring force of respective springs are adjusted equal at the initial condition, the parts will be dislocated gradually as time goes by.
Further, the chip mounter is usually mounted, on a single substrate 6, electronic parts of several tens to several hundreds, and the substrate 6 consists of at least several sheet and at the most of several hundreds or several thousands sheet, thus, it is important to reduce the time for absorbing and mounting the parts. Therefore, it is important to reduce the minimum weight of the head device 10, and to increase the maximum displacing speed of the device 10. However, the device for opening/closing the locator 14 tends to increase the weight and to reduce the displacing speed.
Further, in the prior art device, a parts-absorbing step, an upward-moving step for the spindle 16, an engaging (position adjusting) step for the locator 14, an opening step for the locator 14, a downward-moving step for the spindle 16 and a parts-mounting step are performed sequentially, which increases inevitably the cycle time.
The present invention aims to solve the above described problems in the prior art device, and to provide an electronic parts mounting device not causing dislocation of the parts and reducing largely the mounting time.